1. Filed of the Invention
This invention relates to rotary presses, specifically to web-fed rotary presses, and more specifically to a mechanism in such machines for cutting the continuous web of printed paper into individual sheets and folding the successive sheets into sections or signatures. Still more specifically, the invention deals with improvements in or relating to the jaw cylinder and folding cylinder in the cutting and folding mechanism which coact to crease and fold the sheets.
2. Description of the Prior Art
The cutting and holding mechanism for a web-fed rotary press usually comprises a cutting cylinder in addition to the noted folding cylinder and jaw cylinder. The printed web of paper is first wrapped around part of the folding cylinder in constant rotation and, while being done so, cut into successive sheets by cutting blades on the cutting cylinder which cut the web and dig into counter cutting means on the folding cylinder. The folding cylinder is equipped with folding blades arranged at circumferential spacings on the surface thereof and each extending parallel to the axis of the folding cylinder. Each folding blade is movable radially of the folding cylinder for pushing each sheet into one of cavities formed in the surface of the jaw cylinder at circumferential spacing and each having an opening parallel to the axis of the jaw cylinder, the jaw cylinder being in rolling in close vicinity to the folding cylinder. Each sheet is folded and creased in one of the cavities in the jaw cylinder and thereby carried away from the folding cylinder.
A variety of suggestions have been made as to how to crease the sheet in each cavity in the jaw cylinder. Japanese Unexamined Utility Model Publication Nos. 2-55672 and 60-193365 are hereby cited. The first citation is alike in teaching use of a movable jaw in the form of a flat, elongate plate arranged in each cavity for movement toward and away from a fixed jaw, the latter being one of the pair of confronting walls defining the opening of the cavity. Pushed off the surface of the folding cylinder by one of the folding blades thereon, the sheet together with the folding blade is inserted in part in one of the cavities in the jaw cylinder and therein engaged between the fixed and movable jaws for creasing. Besides being actuated toward and away from the fixed jaw, the movable jaw is sprung to a certain extent toward the fixed jaw to allow for differences in the thickness of sections to be handled and to close the space created in the folded sheet upon withdrawal of the folding blade therefrom.
Japanese Unexamined Utility Model Publication No. 2-55672 differs from the other reference in that either or both of the fixed and movable jaws are stepped to release the extreme edge of the creased sheet from being engaged therebetween. As the folding blade withdraws into the folding cylinder from the cavity in the jaw cylinder following the engagement of the sheet between the fixed and movable jaws, the space created in the folded portion of the sheet is closed by the movable jaw under spring pressure. Thus is the folded sheet creased between the pair of jaws, only with the extreme edge of the fold left unengaged by the stepped jaw or jaws.
An objection to this first prior art device is that when inserted in the cavity by and with the folding blade, the sheet was inserted between, in particular, the folding blade and the fixed jaw throughout its length along the axis of the jaw cylinder, being strongly pressed against them. The sheet was therefore wedged and ironed by the blade and the folding jaw, with the consequent smearing of the printed sheet surfaces superimposed and contacted with each other, by ink offset. Such ink offset was all the more easy to occur because not only the folded sheet but the folding blade too is first caught between the fixed and movable jaws. The sheet is then under greater spring pressure from the movable jaw than when the folding blade is not caught between the jaws.
Japanese Unexamined Utility Model Publication No. 60-193365, on the other hand, adopts, in addition to the fixed and movable jaws, spring-loaded pushpins extending through the movable jaw for pushing the inserted sheet against abutments of polyurethane or like elastic material on the fixed jaw. Each folding blade on the folding cylinder is recessed to permit the pushpins to travel therethrough. The movable jaw is itself also sprung toward the fixed jaw for the same reasons as that of the first cited reference is. The sheet that has been pushed into the cavity is engaged not only between the fixed and movable jaws but, additionally, between the pushpins and the elastic abutments, in order to remain inserted in the cavity during the withdrawal of the folding blade from between the pair of jaws.
Folded upon forced insertion in the cavity in the jaw cylinder by the folding blade on the folding cylinder, the sheet as well as the folding blade is captured between the fixed and movable jaws. Furthermore, only the folded sheet between the these jaws is pressed against the elastic abutments on the fixed jaw by the spring-loaded pushpins. Upon subsequent withdrawal of the folding blade from the cavity, the space thereby created between the folded parts of the sheet is closed by the spring-loaded movable jaw. The sheet is creased by being pressed against the fixed jaw by the movable jaw, besides being urged against the elastic abutments by the pushpins.
This second prior art folding mechanism possesses the same problems concerning ink offset as does the first. Ink offset was particularly prone to occur at the portion of the folded sheet pressed against the elastic abutments on the fixed jaw by the spring-loaded pushpins. These pushpins themselves gave rise to some additional difficulties. First, being left protruding from the movable jaw under spring pressure, the pushpins were liable to be hit by the sheet being pushed into the cavity, with consequent damage to the sheet. Second, the pushpins on being sprung against the abutment via the sheet were easy to create dents in the sheet surface.
These difficulties arising from the spring-loaded pushpins are absent, of course, from the first cited prior art device. But then the sheet that has been creased between the jaws was easy to come out the cavity together with the folding blade upon withdrawal of the latter, resulting in total failure in folding the sheet.
The present invention has it as an object to preclude the trouble, heretofore often encountered in the art, of any undesired ink offset and consequent smearing of the sheets during the insertion of each sheet in the cavity in the jaw cylinder by the folding blade on the folding cylinder, during the forced engagement of the sheet between the fixed and movable jaws, and during the withdrawal of the folding blade from between the jaws.
Another object of the invention is to assure smooth withdrawal of the folding blade from between the fixed and movable jaws without the inconveniences of the concurrent withdrawal or other displacement or disarrangement of the sheet.
Briefly, the present invention may be summarized as a mechanism in a web-fed rotary press for cutting a continuous web of paper into discrete sheets and folding the successive sheets in the middle into the form of signatures. The cutting and folding mechanism comprises a cutting cylinder, a folding cylinder, and a jaw cylinder. The cutting cylinder has a cutting blade which is to be received, with the rotation of the cutting cylinder and the folding cylinder in opposite directions, on a counter cutting means disposed on the peripheral surface of the folding cylinder for cutting the web into successive sheets. The folding cylinder has means such as set of retractable piercing pins for holding each sheet in place on the folding cylinder by the time when the sheet is thereby transported to a position opposite the jaw cylinder, and folding blades arranged parallel to the folding cylinder axis for travel radially of the folding cylinder in order to push each sheet off the surface of the folding cylinder in the middle of the sheet.
The jaw cylinder, to which the invention specifically pertains, has opened in its surface a cavity for receiving the midpart of the sheet that has been pushed as above by the folding blade. Arranged in the cavity, a movable jaw is movable toward and away from a fixed jaw, which is one of the confronting walls parallel to the jaw cylinder axis and defining an opening of the cavity, in order to press the sheet against the fixed jaw for creasing. The fixed jaw has an indentation formed in its surface so as to be in opposed relationship to an insert part of the folding blade on the folding cylinder in the cavity as the folding blade is inserted in the cavity together with the sheet being pushed thereby.
The movable jaw is held retracted from the fixed jaw before insertion of the sheet in the cavity. When pushed into the cavity by the part of folding blade to be inserted in the cavity, the sheet is not pressed hard against the fixed jaw and not ironed since the latter has the indentation formed therein opposite the insert part of folding blade in the cavity. The sheet is not to pressed hard against the fixed jaw and not ironed, because the unindented part of the fixed jaw is opposed to the spacing rather than the insert part of folding blade in the cavity. The sheet is not ruined and the printed surfaces thereof folded, superimposed and contacted each other are therefore not to ink-smeared by unnecessarily forced sliding contact with the fixed jaw and hence to hold the printings thereon unimpaired.
The movable jaw driven toward the fixed jaw with one of the opposed parts of the sheet folded in the midpart is required to move toward the fixed jaw only to an extent necessary to remove the gaps between the insert part of the folding blade in the midpart of the sheet and the part of the sheet opposed thereto. The other part of the sheet are not pressed too hard, either, because they are caught between the fixed and the movable jaw without interposition of the folding blade therebetween. No ink off-set is therefore bound to occur following the engagement of the sheet between the two jaws.
Upon subsequent withdrawal of the folding blade in the cavity from between the opposed parts of the folded midpart of the sheet back into the folding cylinder, the sheet being creased and folded into a signature is held fast between the fixed and the movable jaw. The folding blade will be easy of disengagement from between the folded midpart of the sheet because the insert part of the folding blade has not been caught too hard by the sheet thanks to the indentation in the fixed jaw. There is practically no possibility of the sheet being pulled out the cavity by the withdrawing the folding blade, not either in part or in whole.
Preferably, as in the preferred embodiment to be presented subsequently, the movable jaw may also have an indentation formed in its surface opposite the fixed jaw. Like the fixed jaw indentation, the movable jaw indentation should be placed in opposed relationship to the insert part of the folding blade on the folding cylinder as the folding blade is inserted in the cavity in the jaw cylinder. The sheet will then be not pressed hard against the insert part of folding blade in the cavity when the indented movable jaw is made to move toward the fixed jaw for creasing the sheet, with the consequent reduction of the possibility of ink offset between printed surfaces of the sheet contacted each other. As an additional advantage the folding blade will subsequently withdraw from between the folded sheets even more smoothly and without displacing or disarranging the sheet in so doing.
The above and other objects, features and advantages of this invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiments of the invention.